They weren't extremely religious, they had a new take on what Islam means altogether and they were extreme in that view, they were just a fringe opinion then and a fringe opinion now. Calling them extremely religious is an affront to all the ultra-religious people that lived here peacefully for hundreds of years.

This is my pov as a Hijazi on what happened in the Hijaz;

This started on a much smaller scale before 79, but it really metastasized after. The first thing they did when they took a hold of Hijaz (82-83 and after) was to replace every other Imam and scholar that didn't comply with their twisted view of Islam, with one of their own people, even as a kid in early 90s I thought that one of the main qualifications to be a "mutawa" was to have a Najdi accent, and it went deeper than that, they even replaced judges and school teachers, anyone that was from a different school of thought and had contradictory opinions to theirs would often get ousted and labeld as a misleading ignorant or worse, a heretic, and they paraded them on TV and in Friday sermons as such, they killed the orthodox clergy of Hijaz, suddenly people weren't allowed to lead prayers in any significant mosques or appear on TV, mind you that some of those native Imams took that position from their teachers, and those teachers from their teachers, and so on going back hundreds of years.

My point is that they didn't just fuck up the liberal and secular lifestyle for us, they fucked over everyone, all with the blessings of the government just to keep them in check. Thank God those days are over.